Background. Poor children with asthma have heightened vulnerability to adverse outcomes. Increasing numbers of children covered by Medicaid are being served by managed care organizations (MCOs), whose quality of care deserves more careful evaluation. Hypotheses. We will test a variety of hypotheses relating specific features of MCOs to the quality of care they deliver. For example, we will test whether having asthma-specific provider profiling or a centralized disease management program is associated with better asthma- related quality of life or parent satisfaction. Research Plan. This prospective cohort study will enroll 2,700 Medicaid- insured children with asthma in nine MCO systems in California, Washington, and Massachusetts, and follow them for one year. Data will be collected via parent telephone interviews, primary care provider health plan features such as payment mechanisms, provider profiling and incentives, and disease management programs. Features of care measured at the individual patient level will include accessibility, continuity, and self-care practices. Dependent variables will include asthma- related quality of life, hospitalization and emergency department visits, and antiinflammatory medication use. Covariates will include severity of illness and comorbidities. analyses will use generalized estimating equations and related methods which account for clustering of patients within health plans, provider groups, and individual providers. Policy Implications. By identifying MCO features associated with high quality care, these results will suggest ways to improve care within varying managed care systems.